Less than one nanometer wide - the world's smallest superconductor

The world of superconductors just became a much “smaller” place. Scientists taking part in an Ohio University led study have discovered the world’s smallest superconductor – a sheet of four pairs of molecules measuring less than one nanometer (that's 0.000001 millimeter) wide, potentially paving the way for next – generation
nanoscale electronics.

The findings, published in online journal Nature Nanotechnology, demonstrate the first evidence that nanoscale molecular superconducting wires are able to be fabricated.

“Researchers have said that it is practically impossible to create nanoscale interconnects using metallic conductors because the resistance increases as the size of the wire becomes smaller," says lead author Saw-Wai Hla, an Associate Professor of Physics and Astronomy with Ohio University’s Nanoscale and Quantam Phenomena Institute. "The nanowires become so hot that they can melt and destruct. That issue, Joule heating, has been a major barrier for making nanoscale devices a reality.”

Funded by the U.S. Dept. of Energy, the new study led by Prof. Hlas examined synthesized molecules of the chemical (BETS)2-Gacl4 – a type of organic salt- on a silver substrate. The team observed superconductivity in varying lengths of molecular chains using an imaging method called scanning tunneling spectroscopy (STS).

Superconductors offer zero electrical resistance, which means an electric current flowing through one is able to persist indefinitely with no power source. The team involved had to cool the molecules to a temperature of 10 Kelvin as, even at the macroscale, materials capable of exhibiting these characteristics must be subject to incredibly low temperatures for the effect to become apparent.

The researchers found that superconductivity decreased in chains of less than 50 nanometers in length, however was still present in chains as small as four pairs of molecules.

Prof Hla states that the “study has opened up a new way to understand this phenomenon, which could lead to new materials that could be engineered to work at higher temperatures”, potentially leading to the development of nanoscale electronic devices and energy applications.